Filter with single scalar o/p

[John Biddiscombe]

Dear All,

Suppose you have a filter which takes as input a (possibly very large)
vtkStructuredPoints dataset and generates as its output a single value.
(say) 5.334

Is there any point making this a proper vtkFilter, rather than just a
subroutine in some library of code.

Clearly there's a lot of baggage associated with a vtkFilter - most of
which in this case is not required.

However....
For programs dealing with large quantities of data and using the vtk
Pipeline methodology, it does seem to be a useful thing to have.

2 questions
1) would a StructuredPoints dataset with 1 dimension and 1 scalar be the
best storage facility for this (or a new DatasetToScalar filter superclass)

2) Can anyone suggest a more efficient means of utilizing this kind of
algorithm - by which I mean a better way of generating single valued
outputs without losing the pipeline style.

Perhaps other users have also required a parameter supplied to a filter (eg
SetHeight(...) as opposed to a whole dataset) to change as a result of
other pipeline changes. As yet, there only seems to be an ->Update() on
Filters or ProcessObjects and not to parameters....

Your views appreciated

John B



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